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Test principle and characteristics of residual stress detector

  • Source: Unknown
  • Date: April 28, 2020
  • Number of views: two hundred and five
The measurement methods of residual stress can be divided into two categories: destructive testing and nondestructive testing. The destructive test method is the stress release method, which can also be called the mechanical method; Non destructive method is physical method.
 
remnant Stress detector Test principle
Based on the famous Bragg equation 2dsin θ= n λ ： That is, when a certain wavelength of X-ray is irradiated on the crystal material, the optical path difference of the X-ray diffracted by two adjacent atomic planes is exactly an integral multiple of the wavelength. By measuring the diffraction angle change Δθ So as to obtain the change of lattice spacing Δ d. According to Hooke's law and the principle of elasticity, the residual stress of the material is calculated. (X-ray diffraction method)
The principle of measuring residual stress by blind hole method is shown in the figure below. Assuming that there is a general residual stress field in a certain area of an isotropic material, the maximum and minimum principal stresses are σ 1 and σ 2. Paste a special strain rosette on the surface of the area, punch a small hole in the center of the strain rosette, causing stress release at the hole edge, so as to generate release strain in the strain rosette deletion area. According to the release strain measured by the strain rosette, the residual stress can be calculated: the following figure is the schematic diagram of blind hole method residual stress measurement.
 
In the formula:
ε 1、 ε 2、 ε 3 - Release strain in three directions;
σ 1、 σ 2 - maximum and minimum principal stress;
θ — σ The included angle between No. 1 and the reference axis of No. 1 sheet;
E - elastic modulus of material;
A. B - Two release coefficients.
The A and B coefficients are related to the hole diameter, strain rosette size and hole depth.
 
Residual stress detector characteristic
Taking the full automatic residual stress detector as an example, its characteristics are as follows:
1. Automatic switching and time-sharing measurement of 3-channel static strain
2. The elastic modulus can be set to measure the static stress of various materials
3. It can eliminate the influence of additional strain in drilling, automatically detect, accurately calculate, and display and record residual stress on the LCD（ σ 1、 σ 2、 θ）
4. The blind hole release coefficient can be calculated automatically. It is not only applicable to materials with known blind hole strain release coefficients A and B, but also can be used to convert more accurate coefficients and measure residual stress for materials with unknown blind hole strain release coefficients through relevant theoretical formulas. In fact, A and B of a large number of tested materials are unknown, which is inconvenient or not calibrated by test. If we do not consider A and B, which are very different from each other, the calculation results of residual stress will be completely wrong. Because the strain release coefficients of different materials may vary greatly, this automatic residual stress detector is very convenient and accurate for measuring the residual stress of unknown materials A and B
5. With USB interface, data can be transferred to the outside or sent to PC for reprocessing
6. Mass storage of measurement results and convenient listing, query and printing
7. Embedded printer, online printing results, such as main stress σ 1、 σ 2 and principal stress direction θ
8. Strain gauge sensitivity can be set
9. Poisson's ratio, release coefficient, etc. can be set
10. Massive storage of measurement results and convenient listing, query and printing
11. It adopts 5.7 ″ single LCD screen and special humanized case, which is intuitive and convenient
12. The equipment operation interface adopts the pull-down menu, and it is very convenient to input or query various options and workpiece material parameters
 
The above is the sharing of Dongyi Seiko on the "testing principle and characteristics of residual stress detector". Shenzhen Dongyi Seiko Equipment Co., Ltd. specializes in the supply of stress testers, glass stress testers, Japanese original stress testers, fsm-6000le surface stress testers and other stress detection equipment, and provides professional laboratory solutions and equipment support services. Consulting hotline: 400-992-8117

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